The invention relates to a pole-unit of a medium voltage gas-blast circuit breaker by piston compression of a high dielectric strength gas, notably sulphur hexafluoride, comprising a sealed insulating casing of general cylindrical shape filled with the gas, in which a stationary contact and a movable contact are coaxially arranged, the latter being slidably mounted and bearing a piston, confining, with a transverse subdividing partition of said casing, a compressible volume compressing the puffer gas which blows out the arc drawn when separation of the contacts occurs.
A gas-blast electrical circuit breaker formed by assembly of several pole-units of the kind mentioned enables medium voltage currents to be broken by simple actuation of an operating shaft. Each pole-unit comprises an insulating molded enclosure in the form of a pocket sealed on its open end side by a metal or insulating cover. The structure and arrangement of these state-of-the-art pole-units are complicated and require a large assembly and manufacturing time. In particular, guiding the movable contact rod by a series of V-shaped groove rollers is complicated and costly.
The object of the invention is to achieve a pole-unit with a simplified structure using injected parts, secured by simply clipping them together.